1. Field of the Invention
The present invention relates to a polymer useful for positive photoresist and a positive photoresist composition containing the same.
2. Description of the Prior Art
The high integration of semiconductor devices has always been followed by significant advance in lithography. Using the g-line(wavelength 436 nm) or i-line(wavelength 365 nm) is limited in the preparation the high integration of semiconductor devices. Accordingly, as the light sources used to form the fine patterns become shorter in wavelength from g-line to uv light and deep uv light, excimer laser, such as a KrF laser and ArF laser, and electron beams, the development of the compositions corresponding to the light sources are essential for the lithography.
Active research has been directed to the development of chemical amplified photoresists used deep UV light, further to KrF laser. These photoresist prepared from a compound which generates acid upon radiation(hereinafter referred to as "photoacid generator"), and resin containing high content of acid-decomposable radical.
For example, a photoresist prepared from a matrix resin containing high content of acid-decomposable radical and photoacid generator is disclosed in Japanese Patent Publication No. 27600/1997, Japanese Patent Laid-Open Publication No. 27829/1988, U.S. Pat. No. 5,310,619 and U.S. Pat. No. 4,491,628.
However, these conventional resists show a problem in that desired patterns profile cannot be obtained because the formation of the T-top by the base component in the air, the decrease of the effect of dissolution inhibits developed in alkali solution and the existence of scum after developing, and thermally resistance is poor.